Lubricating oil composition



United States Patent 3,003,963 LUBRICATING OIL COMPOSITION Edward L.Kay, Wappingers Falls, N.Y., assignor t Texaco Inc., a corporation ofDelaware No Drawing. Filed Sept. 30, 1958, Ser. No. 764,244 2 Claims.(Cl. 252-427) This invention relates to a lubricating composition whichis particularly designed for lubrication of modern high speed engines.More particularly, this invention concerns a lubricating oil compositionhaving improved load carrying ability with accompanying resistance tocorrosion and coking.

With the improvement and increase in speeds of newly developed heavyhigh speed machinery, aircraft engines and propulsion engines, it isalways desirable to increase the load carrying ability of thelubricating compositions to be used in the lubrication of such engines.

In accordance with the present invention, an improved lubricatingcomposition having increased load carrying ability with excellentcorrosion and coking resistance is obtained by the inclusion of from 0.1to about 5% of a tetra (C -C alkyl titanate in a lubricating oil.Preferably, a tetra alkyl titanate wherein the alkyl group has from 2 to4 carbon atoms is used in the preferred amounts of from 0.5 to 1.5 wt.percent.

The tetra alkyl titanates include for example, tetramethyl titanate,tetraethyl titanate, tetrapropyl titanate, tetraisopropyl titanate,tetra-n-butyl titanate and isomers, tetra-n-pentyl titanate and isomers,and tetra-n-hexyl titanate and isomers. Of these tetraethyl,tetrapropyl, tetraisopropyl, tetrabutyl and tetraisobutyl titanates arethe preferred additives of the invention.

The lubricating oils of this invention include hydrocarbon lubricatingoils and synthetic lubricating oils. The hydrocarbon oils found to beuseful for this invention include oils having a viscosity in the rangerequired for lubricating fluids and in particular hydrocarbon mineraloils which include paraffin base, naphthene base, mixedparafiin-naphthene base and residual oils. The hydrocarbon lubricatingbase generally has been subjected to solvent refining to improve itsoxidation and thermal stability and viscosity-temperature properties aswell as solvent dewaxing to remove waxy components and to improve thepour of the oil. Broadly speaking, hydrocarbon lubricating oils havingan SUS viscosity at 100 F. of between 50 to 2500 are used in theformulation of the improved lubricants of this invention.

The mineral lubricating oils to which the tetra alkyltitanates of thisinvention are added usually contain other additives designed to impart,desirable properties thereto. For example, viscosity index improverssuch as the polymethacrylates having a molecular weight ranging from 500to 25,000 are usually included therein. The VI improver normally used isa polymethacrylate having the following recurring structural unit:

wherein R is an aliphatic radical ranging from butyl to stearyl and n isan integer of more than 1.

The use of various metal base organic type additives has been foundeffective and are generally incorporated in the lubricating oils of thisinvention, particularly those oils used in high speed, spark ignitionand diesel engines to reduce ring sticking, minimize lacquer formationand carbon deposits. The metal alkyl phenolates wherein the alkyl groupon the benzene nucleus is of comparatively high molecular weight hasbeen found particularly useful where the mineral lubricating oil is ofthe type generally employed for the crankcase lubrication of aircraftengines which normally operate at higher power levels on high octaneairplane fuel. The preferred type of hydroxy aromatic compound is analkyl phenol prepared by alkylating phenol, cresol, xylenol or otheralkyl phenol with an olefin polymer to obtain an alkylated phenolwherein the alkyl constituents on the benzene nucleus contain a total ofat least 15 carbon atoms and preferably at least 18 to 30 carbon atoms.A combination of magnesium and zinc salts of alkyl phenols wherein thealkyl groups have from 18 to 30 carbon atoms has been found particularlyuseful. The magnesium alkyl phenolate is employed within the range of0.5 to 2.0 wt. percent and the zinc alkyl phenolate is employed inconjunction with the magnesium phenolate in a proportion of 0.25 to 1.5percent by wt. on the basis of the total lubricating oil composition.Lubricating oil compositions containing the desired combination ofmagnesium and zinc alkyl phenolates are set forth in U.S. Patent No.2,674,577 to Frederick C.

C. Towne, issued April 6, 1954. I

The hydrocarbon lubricating oils of this invention may also containother useful additives such as metal sulfonates to afford additionaldetergent-dispersant properties, metal dialkyl dithiophosphates toafford additional corrosion and oxidation resistance, anti-foam agentssuch as silicone polymers in the amounts of about 5 to 200 parts permillion, etc.

The synthetic lubricating bases are usually of the ester or ether type.High molecular Weight, high boiling liquid aliphatic esters generallyprepared by reacting 2 moles of a monohydroxy alcohol with an aliphaticdicarboxylic acid, possess excellent viscosity-temperature andlubricating properties and are finding ever increasing utilization inlube Oils adapted for high and low temperature lubrication; esters ofthis type are used in the formulation of jet engine oils. Examples ofthis class of synthetic lubricating bases are the diesters of acids suchas sebacic, adipic, azelaic, alkenyl-succinic, etc.; specific examplesof these diesters are di-2-ethylhexyl sebacate, di-Z-ethylhexyl azelate,di-2-ethylhexyl'adipate, di-n-amyl sebacate, di-Z- ethylhexyl n-dodecylsuccinate, -di-2'-methoxy-2--ethoxyethyl sebacate (the methyl Carbitol'diester), di-2-ethyl- 2-n-butoxyethylsebacate- (theZ-ethyl-butylCellosolve diester), di-Z-n-butoxyethyl azelate (the n-butyl Cellosolvediester), and di-2"-n'-butoxy-2-ethoxyethyl n-octyl succinatc (then-butyl Carbitol diester) Polyester lubricants formed by a reaction ofan aliphatic dicarboxylic acid of the typev previously described, aglycol and an aliphatic monohydroxyl alcohol or an aliphaticmonocarboxylic acid in specified mole ratios are also employed as thesynthetic lubricating, base in the compositions of this invention;polyesters of this type are described in US. 2,628,974. Polyestersformed by reaction of a mixture containing specified amounts of di-Patented Oct. 10, 1961 propylene glycol, sebacic acid and Z-ethylhexanoland of a mixture containing adipic acid, diethylene glycol and 2-ethylhexanoic acid illustrate this class of synthetic polyesterlubricating bases.

Polyalkylene ethers as illustrated by polyglycols are also used as thelubricating base in the compositions of this invention. Polyethyleneglycol, polypropylene glycol, polybutylene glycols and mixedpolyethylene-polypropylene glycols are examples of this class ofsynthetic lubricating bases.

The sulfur analogs of the above-described diesters, polyesters andpolyalkylene ethers are also used in the formulation of the lubricatingcompositions of this invention. Dithioesters are exemplified bydi-Z-ethylhexyl thiosebacate and di-n-octyl thioadipate; polyethylenethioglycol is an example of the sulfur analogs of the polyalkyleneglycols; sulfur analogs of polyesters are exemplified by the reactionproduct of adipic acid, thioglycol and 2-ethylhexyl mercaptan.

To demonstrate the excellent improvement in the loadcarrying ability oflubricating oils containing the tetra alkyl titanates of this invention,a High Speed Gear Scuff Test was used. This test is intended for theevaluation of the scuff-limited load-carrying ability of thoselubricants used in reduction and accessory drives of turbojet andturbo-prop engines. The method of test provides for the running of twospur gears in a Pratt and Whitney Gear and Lubricant Tester (also termedthe Ryder Gear Tester). The oil inlet temperature to the gears was l65i5F. The face width of the driven gear was 0.937 inch and the face widthof the driving gear was 0.25 inch. The dynamometer speed of the geartester was 3830 rpm. (equivalent to a gear speed of 10,000 r.p.m.) andloading pressure of 2 /2 p.s.i. applied during break-in. After runningfor 10 minutes, the tester was shut down and the driving gear removedand an estimate of the percentage of tooth area scuffed on each tooth ofthat gear was made. The gear was replaced and the above procedurecontinuously repeated using a higher loading pressure with increments of5 p.s.i. at each repetition until 22.5 percent of the total tooth facearea on the driving gear had been scuffed, the load corresponding tothis point being considered the scuff load. Scuffing is defined as thatdegree of wear or abrasion which obliterates the axial grinding marks onthe gear tooth. The loading pressures used were as follows: 2.5, 5, 10,15, 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, 70, 75, 80 p.s.i. and up. Atooth load conversion factor of 18.5 sq. in. which was a constantcalculated from measured data from the tester, was multiplied by theloading pressure at the scuff load and divided by the width of thedriving gear (0.25) to obtain the tooth load in pounds per inch. Theresults obtained using the above test procedure on various lubricatingoil compositions including that of the invention are set forth in thefollowing table:

TABLE I High speed gear test Oil: Tooth Load, p.p.i. Base Oil A2,6402,680 Base Oil A+l% (wt.) Tetraisopropyl titanate 7,400-7,250 BaseOil B 3,4403,400 Base Oil B+1% (\vt.) Tetraisopropyl titanate 16,5007,450

1 No scutf evidenced at this load.

The above table indicates the very great and surprising improvement inthe load-carrying ability of the base oil containing tetraisopropyltitanate.

Base oil A consisted of a paraflin base crude residu um which had beenpropane deasphalted, furfural refined, solvent dewaxed and clayfiltered, 16.5% (wt.) of a parafiin base wax distillate which had beenfurfural refined, light acid treated, solvent dewaxed and clay filtered,and 0.1% (wt) of a 40% concentrate of a polymerized ester of methacrylicacid having a molecular weight of from 10,000 to 15,000 in a refinedmineral oil carrier. The gravity in API of this base oil composition was28.2, the SUS viscosity at 210 F. was 97.5 seconds, while the viscosityindex was 100. Base oil B consisted of base oil A plus 2.9% (wt) of amixture of 2 parts of magnesium alkyl phenolate to 1 part zinc alkylphenolate wherein the alkyl groups contained from 18 to 30 carbon atoms.

The load-carrying ability of the composition of the invention was alsodemonstrated in the I.A.E. Gear Test which is one of the requirements ofBritish Specification D.E.R.D. 2487, Lubricating Oil, Aircraft TurbineEngine, Synthetic Type. The I.A.E. Gear Test is also designed toevaluate the scuff-limited, load carrying ability of aircraft gearlubricants.

The results of the I.A.E. Gear Test on lubricating oil compositions ofthe invention are set forth in the following table:

TABLE II I .A.E. gear test Oil" Tooth Load, lbs.

The above table again indicates the improvement afiorded the base oil bythe addition of tetraisopropyl titanate. It also shows the furtherability of the tetra alkyl titanates of the invention to increase theloadcarrying ability of a lubricant composition as greater amounts oftitanate are added thereto.

The excellent corrosion resistance of lubricating oil compositionscontaining the tetra alkyl titanates of the invention was alsodemonstrated in a number of corrosion tests. The tests were performedusing base oils A and C. Base oil C consisted of a paraffin base cruderesiduum which was propane deasphalted, furfural refined, solventdewaxed and clay filtered, 3 (wt) percent of a mixture of 2 partsmagnesium alkyl phenolate to 1 part zinc alkyl phenolatewherein thealkyl groups had from 18 to 30 carbon atoms, and parts per million of a10% dimethyl silicone concentrate in a kerosene carrier as a foaminhibitor.

The S.O.D. Lead Corrosion Test which is described in MilitarySpecification, MILL7808C, Lubricating Oil, Aircraft Turbine Oil,Synthetic Base, dated November 2, 1955, was used to determine thecorrosion resistance of lubricating oil compositions of the invention.

Briefly, The S.O.D. Lead Corrosion Test consists of exposing a leadspecimen to the action of a test lubricant for one hour at 325 F. 1 2 F.in the presence of a copper catalyst. The test lubricant is mechanicallystirred and filtered dry air is introduced into the test lubricant at acontrolled rate. Results are presented as change in weight (mgs.) persquare inch of lead specimen surface area.

TABLE HI S.O.D. lead corrosion test Wt. Loss, mgs. per sq. inch 0.8

Oil:

Base Oil A Base Oil A+l% (wt.) tetraisopropyltitanate 0.4 Base Oil C 0,1Base Oil C+l% ('wt.) tetraisopropyl titanate. 0.02

A lead panel consisting of chemically pure lead approximately l'Vs x 1/4 x inches is immersed in the test lubricant for 48 hours at a test oiltemperature of 200 F. A variation of the test is that 2% water is addedto the test lubricant and adequately emulsified and the emulsionsubjected to above procedure. The test results are expressed as weightchange, (rugs) and are given in the following table:

TABLE IV Lead strip corrosion test Wt. Loss, mgs.

Without With 2% Water Water Base 011 C- 1 70 Base 011 O+1% (wt.)tetraisopropyl titanate 35 In addition, the corrosion resistance of thelubricant composition of this invention was demonstrated in the MacCoullCorrosion Test. The MacCoull Bearing Corrosion Test is described inS.A.E. Transactions, vol. 50 page 8, August 1952, pages 338-345. Theresults of the MacCoull Corrosion Test on a lubricating oil compositionof the invention is demonstrated in the following table:

TABLE V MacCoull bearing corrosion test Cu-Pb Neut. Oil Bearing Hr. No.

Wt. Loss, mgs.

Base Oil 0 33, 80 5. 4 Base 011 (H-1% (wt.) tetralsopropyltitanate- 0,0 1. 4

troleum ether and weighed. The panel is then heated to 600 F. and thetest lubricant continuously splashed on to the surface of the panel fora total of 8 hours. Splashing is effected by rotating a spindle at rpm.in the test lubricant so that a splashing rate 2410.1 grams per minuteis obtained. At the end of 8 hours of splashing, the test panel isremoved, cooled and flushed with petroleum ether and reweighed. Any cokedeposits on the edges of the test panel shall be removed before finalweighing.

The following table shows the results of the above described testprocedure on lubricating oil compositions of the invention.

TABLE VI Panel coking test oil: Deposits, mgs. Base Oil A r 88 Base OilA+l% (wt) tetraisopropyl titanate 6 Base Oil 32 Base Oil C+1% (=Wt.)tetraisopropyl titanate 2 The data presented in the above table areevidence of much improved coking resistance in the lubricating oilcomposition containing the tetraisopropyl titanate.

Obviously, many modifications and variations of the invention ashereinabove described may be made with out departing from the spirit andscope thereof, and therefore, only such limitation should be made as areindicated in the appended claims. 7

I claim:

1. A mineral lubricating oil containing from about 0.5 to 2% by wt. of amagnesium alkyl phenolate wherein the alkyl group has from 15 to 30carbon atoms, from about 0.25 to 1.5% by wt. of a zinc alkyl phenolatewherein the alkyl group has irom 15 to 30 carbon atoms, and from 0.5 to1.5% by wt. of a tetra alkyl titanate wherein the alkyl groups have from2 to 4 carbon atoms.

2. A mineral lubricating oil containing about 3.0 percent by weight of amixture of 2 parts magnesium alkyl phenolate and 1 part zinc alkylphenolate wherein the alkyl groups have from 18 to 30 carbon atoms, andfrom 0.5 to 1.5 percent by weight of tetraisopropyl titanate.

References Cited in the file of this patent UNITED STATES PATENTS Loaneet a1. May 30, 1939

1. A MINERAL LUBRICATING OIL CONTAINING FROM ABOUT 0.5 TO 2% BY WT. OF AMAGNESIUM ALKYL PHONOLATE WHEREIN THE ALKYL GROUP HAS FROM 15 TO 30CARBON ATOMS, FROM ABOUT 0.25 TO 1.5% BY WT. OF A ZINC ALKYL PHENOLATEWHEREIN THE ALKYL GROUP HAS FROM 15 TO 30 CARBON ATOMS, AND FROM 0.5 TO1.5% BY WT. OF A TETRA ALKYL TITANATE WHEREIN THE ALKYL GROUPS HAVE FROM2 TO 4 CARBON ATOMS